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  • 1
    Electronic Resource
    Electronic Resource
    Structural and temporal requirements for geomagnetic field reversal deduced from lava flows (2005)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 434 (2005), S. 633-636 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Reversals of the Earth's magnetic field reflect changes in the geodynamo—flow within the outer core—that generates the field. Constraining core processes or mantle properties that induce or modulate reversals requires knowing the timing and morphology of field changes that ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03431
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    Paper (German National Licenses)
    Fulltext
  • 2
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    40Ar/39Ar age constraints to MIS 5.5 and MIS 5.3 paleo-sea levels: implications for global sea levels and ice-volume estimation (2023)
    PANGAEA
    Details
    Publication Date: 2023-08-31
    Description: We present ten 40Ar/39Ar age determinations, both on primary volcanic deposits and on detrital sanidine, which provide geochronologic control on the MIS 5.5 and MIS 5.3 sea-level indicators that occur at three coastal caves in the central Tyrrhenian Sea of Italy. Samples dated for the present work are as follows: - Two pumice clasts (MOSC-22, MOSC-37) extracted from the sand layers constituting the sedimentary fill of Moscerini Cave, recovered during the original archaeological excavations performed in the year 1949, stored at the IIPU (Istituto Italiano di Paleontolgia Umana) repository in Anagni (Frosinone, italy). These two samples were processed at the rare Gas Laboratory of the University of Wisconsin Madison in March, 2019. - One tephra layer (sample GDC-10) intercalated in the sedimentary fill of Capre Cave collected in June, 2021. - Seven sedimentary sand samples collected at Guattari Cave (GU-1, GU-5, GU-105, GU-116) in June, 2020, and at Capre Cave (GDC-6, GDC-8, GDC-0) in June, 2021 . These dates constrain the age of a Strombus-bearing biodetritic conglomerate associated with a tidal notch occurring at 9.5 m a.s.l. at Cape Circeo between 121.5±5.8 and 116.2±1.2 ka. Moreover, deposition of backbeach deposits intercalated in the sedimentary filling of Guattari and Capre coastal caves is bracketed in the interval 110.4±1.4 ka to 104.9±0.9 ka. Such deposits are directly correlated with a tidal notch at ~2.5 m associated with another biodetritic conglomerate at Cape Circeo. The latter is correlated with the adjacent marine terrace, occurring at 3-5 m in the coast between Capes Circeo and Anzio, for which a maximum age of 100.7±6.6 ka was previously reported. These data provide evidence for a maximum sea level around 9.5 m above the present sea level and a duration of MIS 5.5 highstand until 116 ka, in line with estimation from other regions in the world. In contrast, they suggest a maximum sea level during MIS 5.3 highstand that is similar to the present level, and only ~7 m lower than the MIS 5.5 highstand, challenging the reconstructions of the MIS 5 ice-sheet volumes and derived global sea levels that are based on the benthic oxygen isotope records.
    Keywords: 40Ar/39Ar geochronology; Age, mineral; Age, mineral, standard deviation; Analytical method; Capre_GDC-0; Capre_GDC-10; Capre_GDC-6; Capre_GDC-8; Capre Cave; Comment; DATE/TIME; Elevation of event; Event label; Geological sample; GEOS; Guattari_GU-1; Guattari_GU-105; Guattari_GU-116; Guattari_GU-5; Guattari Cave; Latitude of event; Longitude of event; MIS 5; Moscerini_MOSC-22; Moscerini_MOSC-37; Moscerini Cave; sea level change; Tyrrhenian Sea
    Type: Dataset
    Format: text/tab-separated-values, 40 data points
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    DATA PANGAEA
  • 3
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    Glacier melting triggers massive gravel deposition in central Italy's river basins, unveiling deglacial events from 1.25 to 0.78 Ma (2024)
    PANGAEA
    Details
    Publication Date: 2024-02-08
    Description: We provide a dataset of 40Ar/39Ar age constraints for seven samples of sedimentary deposits recovered from a 120 m deep borehole drilled in the city of Rome in the year 2022. Twenty to thirty sanidine crystals were separated from the sandy matrix of the gravel beds obtained from the borehole. Each gravel bed is part of an aggradational succession deposited in response to sea-level rise in the delta of the Paleo-Tiber River during the late Lower Pleistocene. These aggradational successions are characterized by a sharp boundary that separates a layer of well-rounded limestone and chert pebbles, with diameters reaching up to approximately 10 cm, embedded in a matrix of silty sand (0.5-1.0 mm). This layer is distinct from another layer of mostly clayey (〈0.004 mm) and sandy (〈0.5 mm) sediments that is several meters thick. Based on the conceptual model of aggradational successions proposed by Marra et al. (2016, doi:10.1016/j.epsl.2016.05.037), the sharp sedimentary boundaries are used as a proxy for glacial terminations. The achieved geochronologic constraints allow for an overall good correlation between each aggradational succession, represented by the basal coarse gravel abruptly transitioning to sandy clay sediments, and each period of sea-level rise inferred from the d18O curve in the interval encompassing MIS 19 through MIS 37, 780 through 1250 ka.
    Keywords: According to Jicha et al. (2016); AGE; Age, standard deviation; Date; Drilling/coring; ELEVATION; Event label; Italy; Latitude of event; Longitude of event; Rome_PR1; Rome_PT2; Sample ID; Sample material
    Type: Dataset
    Format: text/tab-separated-values, 32 data points
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    DATA PANGAEA
  • 4
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    Geology and 40Ar/39Ar geochronology of the medium- to high-K Tanaga volcanic cluster, western Aleutians (2012)
    Geological Society of America (GSA)
    Details
    Publication Date: 2012-05-01
    Description: We used geologic mapping and geochemical data augmented by 40Ar/39Ar dating to establish an eruptive chronology for the Tanaga volcanic cluster in the western Aleutian arc. The Tanaga volcanic cluster is unique in comparison to other central and western Aleutian volcanoes in that it consists of three closely spaced, active, volumetrically significant edifices (Sajaka, Tanaga, and Takawangha), the eruptive products of which have unusually high K2O contents. Thirty-five new 40Ar/39Ar ages obtained in two different laboratories constrain the duration of Pleistocene–Holocene subaerial volcanism to younger than 295 ka. The eruptive activity has been mostly continuous for the last 150 k.y., unlike most other well-characterized arc volcanoes, which tend to grow in discrete pulses. More than half of the analyzed Tanaga volcanic cluster lavas are basalts that have erupted throughout the lifetime of the cluster, although a considerable amount of basaltic andesite and basaltic trachyandesite has also been produced since 200 ka. Major- and trace-element variations suggest that magmas from Sajaka and Tanaga volcanoes are likely to have crystallized pyroxene and/or amphibole at greater depths than the older Takawangha magmas, which experienced a larger percentage of plagioclase-dominated fractionation at shallower depths. Magma output from Takawangha has declined over the last 86 k.y. At ca. 19 ka, the focus of magma flux shifted to the west beneath Tanaga and Sajaka volcanoes, where hotter, more mafic magma erupted.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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    PAPER CURRENT
  • 5
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    Ar-Ar age constraints on the timing of Havre Trough opening and magmatism (2019)
    Royal Society of New Zealand
    In:  New Zealand Journal of Geology and Geophysics, 62 (3). pp. 371-377.
    Details
    Publication Date: 2022-01-31
    Description: The age and style of opening of the Havre Trough back-arc system is uncertain due to a lack of geochronologic constraints for the region. 40Ar/39Ar dating of 19 volcanic rocks from across the southern Havre Trough and Kermadec Arc was conducted in three laboratories to provide age constraints on the system. The results are integrated and interpreted as suggesting that this subduction system is young (〈2 Ma) and coeval with opening of the continental Taupo Volcanic Zone of New Zealand. Arc magmatism was broadly concurrent across the breadth of the Havre Trough.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.1080/00288306.2019.1602059
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    New Insights into the Formation and Evelution of the Aleutian Arc (2018)
    In:  [Invited talk] In: AGU Fall Meeting 2018, 10.-14.12.2018, Washington, D.C., USA .
    Details
    Publication Date: 2019-01-11
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Talk
  • 7
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    Optimizing 40Ar/39Ar analyses using an Isotopx NGX-600 mass spectrometer (2022)
    Elsevier
    Details
    Publication Date: 2024-02-07
    Description: 40Ar/39Ar geochronology relies on magnetic sector mass spectrometers to determine relative isotopic abundances. Ongoing technological developments within noble gas mass spectrometers over the last decade have led to analysis of increasingly smaller samples and higher precision, but also result in more complex data correction and interpretation. We describe a new multi-collector noble gas spectrometer, the Isotopx NGX-600, that is configured to optimize 40Ar/39Ar measurements. The NGX-600 is equipped with 9 Faraday collectors and one ion counting electron multiplier. Each Faraday is equipped with Isotopx ATONA® amplifier technology, enabling measurements spanning a dynamic range of amplified beam current from below 10−16 A to above 10−9 A. The performance of the NGX-600 is evaluated using both a conventional Nier-type ion source, and a next generation low temperature ion source, which allows for trap current variation from 200 μA to 1000 μA. We have performed over 3000 analyses of atmospheric argon to: (1) assess optimal measurement and integration times for blanks, baselines, and air aliquots of various ion intensities, (2) quantify the sensitivity via measurements of first principles 40Ar/39Ar standards, (3) compare the sensitivity between the conventional and new low temperature Nier-type ion sources, and (4) evaluate corrections associated with inter-Faraday biases, instrumental mass bias, and Faraday-multiplier gain. In addition to optimization experiments, we report a comparative analysis of both single crystal fusion and incremental heating data from Quaternary volcanic rocks obtained using both the 5-collector Nu Instruments Noblesse and the NGX-600 spectrometers.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    40Ar/39Ar ages and bulk-rock chemistry of the lower submarine units of the central and western Aleutian Arc (2021)
    Elsevier
    Details
    Publication Date: 2024-02-07
    Description: Highlights • The revised minimum subduction initiation age for the Aleutian system is 48 Ma. • The evolution of the arc was characterized by three distinct magmatic pulses. • The types of magmas erupted appear to have changed during the arc evolution. In order to further constrain the timing of the Aleutian Arc initiation as well as its early evolution, an extensive 40Ar/39Ar dating and geochemical (major and selected trace elements) campaign (40 samples) of the lower units of the Aleutian ridge has been carried out on samples dredged from deep fore-arc canyons and rear arc tectonic structures. The new dataset slightly increases the minimum inception age for the Aleutian system, with the two oldest samples dated at 46.1 ± 3.3 Ma and 47.80 ± 0.57 Ma. Both mid Eocene ages were obtained on tholeiitic mafic volcanic rocks from the western section of the arc. The new data also support the occurrence of three distinct periods of enhanced magmatic activity (magmatic pulses) during the pre-Quaternary evolution of the arc (at 38–27, 16–11 and 6–0 Ma), as previously suggested based on a more limited and dominantly subaerial dataset. Moreover, the data refine the duration of the first pulse of activity, which ended 2 Ma later than previous estimates. The first and last pulses may be associated with rotations of the subducting plates while the second pulse might result from regional tectonic changes. The significant overlap between the age distribution of the submarine and subaerial samples suggests that much of the earlier parts of the arc may have been uplifted and subaerially exposed. The expected crustal growth associated with the pulses is unlikely to have significantly impacted magmatic residence times, since no variation in the degree of differentiation of the rocks can be observed during or after the pulses. On the other hand, the type of magmas erupted may have changed during the arc evolution. Prior to the first pulse, activity appears to have been dominantly tholeiitic. On the other hand, the first pulse was characterized by coeval tholeiitic, transitional and calc-alkaline magmas, with calc-alkaline activity increasing after the first ~3 Ma. Subsequently, a dominantly calc-alkaline period occurred from 29 to 8 Ma, followed by a progressive return of coeval tholeiitic, transitional and calc-alkaline activity. These temporal changes in magma types correspond to likely variations in arc crustal thickness beneath the active front, and could therefore be a response to physical changes of the overriding plate.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: archive
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Mineralogy and geochemistry of lavas from the submarine lower caldera walls of Santorini Volcano (Greece) (2022)
    Elsevier
    Details
    Publication Date: 2024-02-07
    Description: Santorini Volcano, located in the central sector of the South Aegean volcanic arc, is one of the most active and potentially dangerous volcanoes in Europe. It has hosted Plinian eruptions over the last 350 ka of which at least four eruptions were accompanied by caldera collapses. Even though Santorini Volcano is considered a major threat, the main focus of research, thus far, has been on the comparatively young and subaerial deposits, whereas older stages of volcanism have been poorly studied. Our study focusses on samples from the submarine inner caldera walls and gives new insights into the early evolutionary stages of Santorini Volcano, contributing to a better understanding of its eruptive history and thus potential risks. The submarine lava successions were sampled along the inner caldera wall by a remotely operated vehicle (ROV) during R/V POSEIDON cruise 511 in 2017. The recovered lavas comprise two magmatic series, a low-K basaltic series overlain by a medium- to high-K series, which includes basaltic andesites, andesites and occasional dacites to trachytes. Major and trace element compositions and mineral zonation patterns suggest that fractional crystallisation and periodic magma replenishment were the dominant processes controlling magma evolution of both magmatic series. In addition, repeated magma mixing events played an important role, as indicated by zonation patterns in plagioclase and clinopyroxene ante- and phenocrysts. The thickness of the submarine lava successions (≥100 m) and the occurrence of similarly zoned plagioclase throughout, indicate long-lived magma plumbing systems characterised by repeated processes. Furthermore, the incompatible element and radiogenic isotope ratios indicate a heterogeneous mantle source for Santorini magmas, which reflects the relative contribution of subduction (sedimentary) input and mantle wedge influx. A lava sample from the northern submarine caldera wall probably represents a deep level of the original Peristeria volcano. 40Ar/39Ar dating of andesite lavas from the southern submarine caldera produced ages of ~255 ka, whereas one basalt lava produced an age of 309 ± 30 ka. Interestingly, the new ages of both groups fall within an age gap in the volcanic history of Santorini Volcano. Even though it was not possible to unequivocally correlate the sampled submarine lava series to known subaerial units, the major and trace element compositions, and Sr-Nd-Pb isotopic compositions of our intermediate lavas show a strong similarity to subaerial lavas of Peristeria volcano, the second oldest major stage of Santorini volcanism. Nevertheless, it seems more likely that we have sampled so far unknown stages of volcanism at Santorini Volcano.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Nature Northwest Pacific altered oceanic crust and implications for arc magmatism (2022)
    Details
    Publication Date: 2023-01-17
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Conference paper
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